The present invention relates to pan heads, are in particular for film or television cameras.
Such a pan head is known, for example, from the German Patent No. 26 57 692 and its corresponding U.S. Pat. No. 4,226,303, as well as the German Patent No. 3,908,682 and its corresponding published UK patent application No. 2,231,548, the disclosures of which are incorporated herein by reference. This pan head serves to rotate a film or television camera about two mutually perpendicular axes, namely a horizontal pitch axis and a vertical swivel axis. Pan heads also serve to hold other, e.g. optical, devices.
To permit soft swivel movements, pan heads are generally provided with a damping means, e.g. a plurality of hydraulic damping units, as described in the above patent.
Such pan heads are also frequently provided with compensating devices for compensating the torque of the fitted device in essentially all rotary positions about the pitch axis; such an arrangement is known, for example, from the German Patent No. 30 26 379 and its corresponding U.S. Pat. No. 4,447,083, the disclosures of which are incorporated herein by reference. In this known pan head the compensating device is a spring assembly. It is important for a uniform swivel that the device fitted on the pan head is "balanced" in the resting position, i.e., that when the common mass center of the rotor and the device is located vertically above the pitch axis, no torque is produced by the spring assembly. When the pan head is inclined out of the resting position, equal torques or pitching moments then exist in both directions if there are equal and opposite angles of rotation, these moments being compensated by equally great load moments produced by the spring assembly so that the device is kept in balance in virtually every pitching position. The operator thus requires only little force to rotate the device.
The German Patent No. 27 17 772, that likewise describes a compensating device for a pan head, discloses balancing a film or television camera by demounting the compensating device, a spring assembly, while the pan head is held approximately in the resting position, then exactly determining the resting position and finally mounting the spring assembly again between the rotor and the stator of the pan head in the resting position. The determination of the resting position--i.e., the balancing--requires sensitivity on the part of the operator since the exact resting position in which the camera is in unstable balance with the compensating device demounted must be "felt", so to speak, by carefully swiveling the rotor.
In the resting position the camera, or its optical axis, should also be kept horizontal. For this purpose it is known to keep the camera on the rotor in a slide assembly and to shift it when the slide assembly is in a horizontal position until zero torque is "felt". The mass center of the rotor and the camera is then located vertically above the pitch axis. This method is as elaborate as that mentioned above and again requires sensitivity and time. These two methods can of course also be combined.